The killer of an 11-year-old school boy who vanished from the streets of Rockingham more than 20 years ago should be “hunted down” and not left unpunished says Premier Mark McGowan.

Police have reopened the cold case of Gerard Ross, who went missing while on holidays in the seaside suburb in 1997 before his body was found two weeks after he was last seen, which is the subject of a special investigative series titled The Boy in the Blue Cap for thewest.com.au.

Mr McGowan has been the local MP for Rockingham since 1996 and said he remembered days of Gerard’s disappearance vividly.

“I met his family, I met the police officers who were investigating,” he said.

“For the family’s sake I would like to see the case solved.

“It must be terribly traumatic for those people to know that their son’s killer is still out there.”

Mr McGowan said he supported the amount of resources being put in by WA Police to solve the case.

“Murder is the worst crime there is and murdering a little boy in plain daylight on a suburban street is appalling,” he said.

“We need to send a message to people that if you commit these sorts of crimes you can be hunted down decades later and I hope the police are successful.”

The Special Crime division is undertaking a full review and reinvestigation into Gerard’s disappearance and murder.

More than 1300 people have been nominated as having a possible involvement in the 11-year-old’s death.